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Biomedical subjects

Mathias Müller

Publications and source records attributed to Mathias Müller.

28 records · Page 2Linked to original sources
PubMed2003

Phosphorylation of the Stat1 transactivation domain is required for full-fledged IFN-gamma-dependent innate immunity.

Stat1 is phosphorylated on serine 727 within its transactivating domain (TAD) in response to interferons or other immunological signals. We generated gene-targeted mutant mice expressing a serine727-alanine mutant of Stat1. These animals showed increased mortality upon infection with Listeria monocytogenes and impaired clearance of the bacteria from spleen and liver. The Stat1S727A mice were more resistant to the LPS-induced septic shock syndrome, suggesting that Stat1 serine phosphorylation promotes inflammatory responses. Expression of IFN-gamma-induced genes was strongly reduced in macrophages expressing Stat1(S727A). While mutation of Stat1 at S727 did not reduce its binding to chromatin, association with the coactivator CBP and histone acetylation at the interferon-responsive GBP promoter was strongly reduced, suggesting defective recruitment of histone acetylases as the mechanism underlying IFN-gamma hyporesponsiveness. Our data demonstrate that the increase in transcription factor activity caused by Stat serine phosphorylation contributes to macrophage activation and to IFN-gamma-dependent immune responses in vivo.

Amino Acid Substitution↗
PubMed2003

Recombination analysis of human-tropic porcine endogenous retroviruses.

Prevention of cross-species infection of porcine endogenous retroviruses (PERV) is crucial for xenotransplantation. The potential risk of infection is caused by replication-competent PERV as well as by hybrid viruses derived from recombination events of distinct PERV genomes. Recently, human-tropic, replication-competent PERV genomes obtaining hybrid sequences have been observed. Here, complete polymorphism pattern analysis was performed on the full-length PERV gamma1 clones and on the complete envelope (env) gene sequences published to date. Several recombined full-length clones and a high number of different recombination patterns in the env gene were identified. In addition, recombinations with retroviral genomes not yet known were found. Thus, the potential risk of infection also exists for recombination products, including defective PERV loci.

Animals↗
PubMed2003

Characterization of endogenous retroviruses in sheep.

Endogenous retrovirus (ERV) sequences have been found in all mammals. In vitro and in vivo experiments revealed ERV activation and cross-species infection in several species. Sheep (Ovis aries) are used for various biotechnological purposes; however, they have not yet been comprehensively screened for ERV sequences. Therefore, the aim of the study was to classify the ERV sequences in the ovine genome (OERV) by analyzing the retroviral pro-pol sequences. Three OERV beta families and nine OERV gamma families were revealed. Novel open reading frames (ORF) in the amplified proviral fragment were found in one OERV beta family and two OERV gamma families. Hybrid OERV produced by putative recombination events were not detected. Quantitative analysis of the OERV sequences in the ovine genome revealed no relevant variations in the endogenous retroviral loads of different breeds. Expression analysis of different tissues from fetal and pregnant sheep detected mRNA from both gammaretrovirus families, showing ORF fragments. Thus, the release of retroviruses from sheep cells cannot be excluded.

Animals↗
PubMed2002

Production of type I IFN sensitizes macrophages to cell death induced by Listeria monocytogenes.

Type I IFNs (IFN-alpha/beta) modulate innate immune responses. Here we show activation of transcription factor IFN regulatory factor 3, the synthesis of large amounts of IFN-beta mRNA, and type I IFN signal transduction in macrophages infected with Listeria monocytogenes. Expression of the bacterial virulence protein listeriolysin O was necessary, but not sufficient, for efficient IFN-beta production. Signaling through a pathway involving the type I IFN receptor and Stat1 sensitized macrophages to L. monocytogenes-induced cell death in a manner not requiring inducible NO synthase (nitric oxide synthase 2) or protein kinase R, potential effectors of type I IFN action during microbial infections. The data stress the importance of type I IFN for the course of infections with intracellular bacteria and suggest that factors other than listeriolysin O contribute to macrophage death during Listeria infection.

Animals↗
PubMed2002

Reduced body growth and excessive incisor length in insertional mutants mapping to mouse Chromosome 13.

Phenotypic and molecular genetic examinations of a transgenic mouse line showing developmental defects caused by a recessive insertional mutation were carried out. The mutant phenotype is characterized by general retardation of postnatal body growth and by the appearance of increased incisor length in the upper and lower jaw. The mutation causing the aberrant phenotype was mapped to Chromosome 13, 40 cM. Examination of the expression of the candidate genes did not show any alterations. This mutant mouse line provides a reproducible model for the identification and examination of gene(s) involved in growth and in the craniofacial development, including that of the jaws and teeth.

Animals↗
PubMed2002

The murine whey acidic protein promoter directs expression to human mammary tumors after retroviral transduction.

The whey acidic protein (WAP) promoter is known to be active in pregnant and lactating mammary epithelial cells as well as mammary tumors of mice. Here we show that a proximal fragment of the murine WAP promoter, including most elements postulated as being responsible for mammary-specific regulation, confers mammary-specific expression upon a marker gene in transgenic mice even though the distal promoter region, known to be important for rat WAP promoter activity, is lacking. The relatively small size of this fragment allows its insertion into a murine leukemia virus-based retroviral vector in place of the viral promoter. Infection of a number of established human mammary and nonmammary cell lines with such a retroviral vector revealed that the WAP promoter was limited in its activity to mammary tumor cell lines. Expression in tumorigenic mammary cells was even more pronounced when these cells were introduced into the mammary fat pads of mice. This is the first demonstration that the WAP promoter is active in human mammary cells and mammary tumor cells in general, and suggests that the extended proximal WAP promoter may be useful for directing therapeutic gene expression to human mammary tumors.

3T3 Cells↗
PubMed2002

Coexistence of Bos taurus and B. indicus mitochondrial DNAs in nuclear transfer-derived somatic cattle clones.

We investigated the mitochondrial DNA (mtDNA) composition in one of the largest adult somatic mammalian clones (n = 20) reported so far. The healthy cloned cattle were derived from nuclear transfer of an identical nuclear genetic background (mural granulosa donor cells including surrounding cytoplasm) into enucleated oocytes with either Bos indicus or B. taurus mtDNA. Here we report the first cases of coexisting mtDNAs of two closely related subspecies following nuclear transfer. Heteroplasmy (0.6-2.8%) was found in 4 out of 11 cross-subspecies cloned cattle. Quantitation was performed using "amplification refractory mutation system (ARMS) allele-specific real-time PCR." We determined that the ratio of donor cell to recipient cytoplast mtDNA copy number was 0.9% before nuclear transfer. Therefore, we concluded that the percentage of donor cell mtDNA in the heteroplasmic intersubspecific cloned animals is in accordance with neutral transmission of donor mtDNA. We determined an amino acid sequence divergence of up to 1.3% for the two subspecies-specific mtDNA haplotypes. In addition, intrasubspecific B. indicus heteroplasmy of approximately 1% (but up to 7.3 and 12.7% in muscle and follicular cells of one animal) was detected in 7 out of the 9 B. indicus intrasubspecific cloned cattle.

Animals↗
PubMed2002

Characterization of porcine endogenous retrovirus gamma pro-pol nucleotide sequences.

Endogenous retroviral sequences in the pig genome (PERV) represent a potential infectious risk in xenotransplantation. All known infectious PERV have been asssigned to the PERV gamma1 family, consisting of the subfamilies A, B, and C. The aim of the study was the concise examination of PERV gamma by the analysis of the retroviral pro-pol sequences. The analysis of 52 pro-pol clones amplified in this study revealed eight PERV gamma families. In addition to four already-described families (gamma1, gamma4, gamma5, gamma6), four novel families (gamma7, gamma8, gamma9, gamma10) were identified. Quantitative analysis of the novel PERV gamma sequences in selected breeds revealed variations in the endogenous retroviral load. Open reading frames (ORF) in the amplified proviral fragment were only found for PERV gamma1. In addition, novel ORF-containing PERV gamma1 clones consisting of hybrid sequences were revealed. Sequence comparison from published full-length PERV gamma1 clones of the PERV subfamilies A, B, and C resulted in a lack of strict correlation of the classification of pro-pol and env. The results indicated the occurrence of causative recombination events between retroviral genomes. Thus, our study on PERV gamma provides new data for the evaluation and selection of pigs intended to be used in xenotransplantation.

Animals↗
PubMedDate not supplied

Somatic gene transfer into the lactating ovine mammary gland.

BACKGROUND: Somatic gene therapy requires safe and efficient techniques for the gene transfer procedure. The ovine mammary gland is described as a model system for the evaluation of somatic gene transfer methods. METHODS: Different gene delivery formulations were retrogradely injected into the mammary gland of lactating sheep. The efficiency of the gene transfer was subsequently measured by the detection of the secreted transgene products in the milk. To counteract the milk flow in the lactating gland caused by the permanent milk production, a newly developed pretreatment of the mammary gland with hyperosmotic solutions was applied. In addition, in vivo electroporation of DNA into the mammary gland is described. RESULTS: Gene transfer using naked DNA or simple complexes of DNA with polycations did not result in traceable amounts of reporter gene products. However, utilizing the complex cationic lipid DOSPER, a peak expression of about 400 ng/ml was observed 6 days after transfection. Maximum expression rates of more than 1 microg/ml were obtained by combining hyperosmotic pretreatment and receptor-mediated gene transfer. For the in vivo electroporation, the proof of principle for this technique in the mammary gland is reported. CONCLUSIONS: The ovine mammary gland turned out to be a very well suited as a model system for evaluation and optimization of various gene transfer protocols.

Animals↗